Question

срочно нужно 1 вариант ...... ДАЮ 50 баллов​

Answer 1

Ответ:

Объяснение:

1.

$frac{x+7}{x-2}$      ОДЗ: x-2≠0     x≠2    ⇒    x∈(-∞;2)U(2;+∞).

2.

$frac{5-a}{a^{2} -8a+16} +frac{6}{5a-20} =frac{5-a}{(a-4)^{2} } +frac{6}{5*(a-4)} =frac{(5-a)*5+6*(a-4)}{5*(a-4)^{2} } =\=frac{25-5a+6a-24}{5*(a-4)^{2} } =frac{a+1}{5*(a-4)^{2} } .$

3.

$frac{5x^{2}-10xy+5y^{2} }{2x^{2} -2xy+2y^{2} } :frac{4x-4y}{10x^{3} +10y^{3} } =frac{5*(x^{2}-2xy+y^{2}) }{2*(x^{2} -xy+y^{2}) } *frac{10*(x^{3} +y^{3})}{ 4*(x-y)} =frac{5*(x-y)^{2} *10*(x+y)*(x^{2} -xy+y^{2}) }{2*(x^{2}-xy+y^{2} )*4*(x-y) } =\=frac{25*(x-y)*(x+y)}{4} =frac{25*(x^{2} -y^{2}) }{4}=frac{25*(7^{2}-3^{2}) }{4} =frac{25*(49-9)}{4} =frac{25*40}{4} =25*10=250.$4.

$frac{a}{b} =3;frac{b}{c} =8\frac{a}{b}*frac{b}{c} =24\frac{a}{c} =24.$